A Blood-Brain-Barrier-Penetrating Anti-human Transferrin Receptor Antibody Fusion Protein for Neuronopathic Mucopolysaccharidosis II

Abstract

Mucopolysaccharidosis II (MPS II) is an X-linked recessive lysosomal storage disease caused by mutations in the iduronate-2-sulfatase (IDS) gene. Since IDS catalyzes the degradation of glycosaminoglycans (GAGs), deficiency in this enzyme leads to accumulation of GAGs in most cells in all tissues and organs, resulting in severe somatic and neurological disorders. Although enzyme replacement therapy with human IDS (hIDS) has been used for the treatment of MPS II, this therapy is not effective for defects in the CNS mainly because the enzyme cannot cross the blood-brain barrier (BBB). Here, we developed a BBB-penetrating fusion protein, JR-141, which consists of an anti-human transferrin receptor (hTfR) antibody and intact hIDS. The TfR-mediated incorporation of JR-141 was confirmed by using human fibroblasts in vitro. When administrated intravenously to hTfR knockin mice or monkeys, JR-141, but not naked hIDS, was detected in the brain. In addition, the intravenous administration of JR-141 reduced the accumulation of GAGs both in the peripheral tissues and in the brain of hTfR knockin mice lacking Ids, an animal model of MPS II. These data provide a proof of concept for the translation of JR-141 to clinical study for the treatment of patients with MPS II with CNS disorders.

Keywords: blood-brain barrier; enzyme replacement therapy; glycosaminoglycans; iduronate-2-sulfatase; lysosomal storage disease; mucopolysaccharidosis II; transferrin receptor.

Figure 1

Binding Affinities of the anti-hTfR Antibody-Fused hIDS for TfRs and Human hM6PR (A) Schematic representation of JR-141, an anti-hTfR antibody-fused hIDS used in this study. (B) Affinity of JR-141 for human and monkey TfRs and human M6PR. Affinity of naked hIDS for human M6PR is also shown (mean ± SD, n = 3). k_on, association rate constant; k_off, dissociation rate constant; K_D, equilibrium dissociation constant.

Figure 2

The Receptor-Mediated Incorporation into Fibroblasts (A) Concentration-dependent incorporation of JR-141 or naked hIDS into CCD-1076Sk human fibroblasts determined by electrochemiluminescent immunoassay using the anti-hIDS monoclonal antibodies. The incubation time was 20 hr. The values were normalized by the amount of total cellular protein (mean ± SD, n = 3). (B) Inhibition of JR-141 incorporation by M6P (10 mM) or the humanized anti-hTfR monoclonal antibody (400 μg/mL). The concentration of the drugs used in this experiment was 20 μg/mL. The calculated molecular weights (without sugar chains) of JR-141 and naked hIDS are 265,110.93 and 59,274.99, respectively.

Figure 3

Distribution of JR-141 in TFRC-KI Mice after Intravenous Administration (A and B) Pharmacokinetics of JR-141 and naked hIDS in the plasma (A) and the brain homogenates (B). Either JR-141 or the naked enzyme was intravenously administered at a dose of 1 mg/kg. The concentrations of these recombinant proteins were determined by electrochemiluminescent immunoassay (mean ± SD, n = 3; *p < 0.05, ***p < 0.001, t test). Concentrations of the naked hIDS in the brain were incidentally detected at low level in only one animal 1 hr after administration. Statistical analysis was performed using the lower limit value of detection for other animals and other time points. See Table S1 for detailed pharmacokinetic parameters with moment analysis and Figure S2 for distribution of JR-141 and hIDS in peripheral tissues. (C) Immunohistochemical analysis in the brain of TFRC-KI mice 24 hr after intravenous injection of JR-141 or naked hIDS. Arrows indicate Purkinje cells. Scale bars, 20 μm. (D) In vivo imaging of the mice using IVIS Lumina III. Images were acquired at 24 hr after intravenous injection of JR-141 or hIDS. (E) Ex vivo imaging of resected brains after saline perfusion. Color bars indicate radiant efficiency ([p/s/cm²/sr]/[mW/cm²]).

Figure 4

Distribution of JR-141 in Cynomolgus Monkeys after Intravenous Administration (A) Pharmacokinetics of JR-141 in the plasma of the monkey. JR-141 was administered intravenously at a dose of 5 mg/kg (0–8 hr, n = 4; 12 and 24 hr, n = 2). Data were plotted as mean ± SD. Detailed pharmacokinetic parameters are presented in Table S2. (B and C) Concentrations of JR-141 in the peripheral tissues (B) and the brain and spinal cord (C). The heart, kidney, liver, lung, spleen, cerebral cortex, cerebellum, hippocampus, and spinal cord were resected. JR-141 in each tissue homogenate was quantified by electrochemiluminescent immunoassay (n = 2). Bars indicate the mean. (D) Immunohistochemical analysis of the cerebellum. Arrows indicate Purkinje cells. (E) Immunohistochemical analysis of the hippocampus. Arrows indicate the pyramidal cells. The brains were resected at 8 hr after the administration. Scale bars, 20 μm.

Figure 5

Reduction in Accumulation of GAGs by JR-141 in the Brain and the Peripheral Tissues of TFRC-KI/Ids-KO Double-Mutant Mice JR-141 was intravenously administered to the mice at a dose of 1, 3, or 10 mg/kg BW once a week for 4 weeks. GAGs were quantified 1 week after the final dosing in the resected brain, heart, kidney, liver, lung, and spleen. Values are expressed as % accumulation when mean GAG levels in the WT mice were considered to be 0% and those in Ids-KO mice were considered to be 100%. Bars indicate the mean for each group (n = 4). **p < 0.01 by Dunnett test (Ids-KO versus JR-141 groups) and ^##p < 0.01 by Student’s t test (Ids-KO versus hIDS groups). N.S., not significant. The absolute values of the concentration and detailed statistical analysis between groups are presented in Table S3.